Restoring the stability of deteriorated smokeless powder



Patented Mar. 21, 1939 RESTORING THE STABILITY OF DETEBI- ORATED SMOKELESS POWDER.

Alpheus M. Ball, Newark, Del., assig'nor to Hercules Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application December 10, 1937,

Serial No. 179,199 I 4 Claims.

This invention relates to a method for restoring the chemical stability of nitrocellulose smokeless powder which has undergone deterioration during storage.

There are available, large quantities of smokeless cannon powder of the so-called Pyro type containing approximately 99% nitrocellulose and 1% diphenylamine, the former having a nitrogen content of about 12.5 to 12.7% and which is almost completely soluble in a mixture of two parts by volume of ethyl ether and'one part by volume of ethyl alcohol. Most of the powder available was made during the World War and since it is a well-known fact that smokeless powder deteriorates during storage, Pyro cannon powder made under the stress of war time conditions particularly so, it follows that, after nearly 20 years, such powder is of quite low stability so that it is no longer safe to load it into ammunition. In view of the availability and relative cheapness it is not surprising that various methods have been devised in the past to restore chemical stability to this powder.

One of these methods involved grinding the powder grains to a relatively fine state under water and then subjecting this finely divided material to repeated washings with cold water and/or boiling in water, in order to remove the decomposition products. This process has the disadvantage that a great many water washes are required to raise the stability of the powder materially and unless this is done, the reworked smokeless powder has a relatively limited storage life. Furthermore, each time that a water wash is decanted from the powder, a certain amount of the finer powder is carried away, thus resulting in an economic loss. In order to Work this stock into new powder it is necessary that this powder be dried or dehydrated with alcohol, which introduces an additional step.

Another method proposed for restoring the chemical stability of deteriorated smokeless powder is that of covering the Pyro powder grains with ethyl alcohol, allowing them to soak for a period of time at room temperatures, and then gradually raising the alcohol to the boiling point, using apparatus fitted with a suitable refluxing arrangement. The powder grains are subjected to repeated extractions, using preferably hot, fresh alcohol for each extraction, thereby removing substantially all of the diphenylamine and derivatives thereof as well as deterioration products. The diphenylamine removed, is subsequently re-incorpcrated by suitable means.

Extraction with cold alcohol has also been proposed but this as well as the above process has obvious disadvantages. Cold extraction, for example, requires a long time and a large amount of equipment is necessary to purify an appreciable quantity of powder. The hot process involves the settingup of stills for the refluxing of alcohol and, furthermore, involves the hazard of handling hot alcohol. v

Now, I have found that I may restore the chemical stability of smokeless powder of the Pyro type, which has undergone deterioration during storage, by the simple expedient of treating the ground or cracked powder with alcohol under pressure for a short period of time, thereby obtaining powder of satisfactory stability, when dried, which can be used as such for loading certain types of ammunition. Alternatively the ground or cracked powder obtained alcohol wet from the press can be mixed with new nitrocellulose and put through the regular smokeless powder process, or it can be re-worked in the latter process without the addition of new nitrocellulose. For all but the most unstable powders, I prefer treating with alcohol at room temperatures.

In proceeding in accordance with my invention, smokeless powder of the Pyro type, ground under water to a fineness such that it will pass an 8 mesh screen and be retained on a 200 mesh screen, or smokeless powder grains cracked in a suitable manner, is placed in a suitable press, such as, for example, a regular dehydrating press used in nitrocellulose plants for'the dehydration of water wet nitrocellulose with alcohol, and subjected to a pressure of about 200 pounds per square inch to remove the excess water. While maintaining the ground or cracked powder under this pressure, a quantity of ethyl alcohol is pumped in, which is preferably of a strength not less than about 80% ethyl alcohol by volume.'

A pressure of approximately 3000 to 4000 pounds per square inch is then applied and maintained for about V to 5 minutes. the top of the block is then opened and the same pressure maintained for about to 5 minutes more in order to eliminate the excess alcohol. The purified ground or cracked smokeless powder The outlet valve at i isthen removed, the whole operation being pe'rformed in about A to 10 minutes. The powder so obtained will be found to have a material improvement in stability, as will be shown hereafter in detail. Y

Having now described my invention in a general manner, I will now proceed to amore detailed description thereof with reference to the following examples.

' Example I (1) Thirteen pounds of scrap cannon powder, ground under water to a fineness such that it will pass a 35 mesh screen, was placed in a press used for the dehydration of nitrocellulose and put under a pressure of approximately 180 to 200 pounds per square inch to remove the excess water. While maintained under this pressure,

with all outlets'from the press closed, gallons oi. 95% denatured ethyl alcohol were pumped into the powder, after which a pressure of 3500 pounds per square inch was applied and maintained for about one minute. The outlet valve of the press was then opened and the same pressure applied for about one minute more in order to eliminate the excess ethyl alcohol.

(2) A second portion of the same powder, ground as indicated above, was also given a treatment consisting of two cold water washes, each of one-half hour duration, with a change of water between the washes, followed by a boiling treatment of two hours and then by cold water washes of one-half hour each, allowing settling and changing the water between each wash.

(3) Some of the powder, purified by the water treatment as, shown in (2) above was also subjected to the alcohol treatment as outlined in (1) above.

The stability of the powder before treatment and after the various treatments as above shown, is given in the table below.

German test at 134.5"f C. Minutes or turning Treatment of standard methyl violet paper 1 Untreated (ground) 2 Alcohol under pressure.. 3 Water treatments 42 4 As in (3) plus alcohol treatment 42 Example II German test at 134.5" 0. Minutes for turning Tmatment of standard methyl violet paper 1 Untreated (ground) 34 2 Alcohol under pressure 43 3 Water treatment plus alcohol under pres- 43 sure It will be understood that, in all cases, the samples of powder are dried before undergoing the German test.

From the above results it is apparent that the process in accordance with my invention raises the stability of a deteriorated smokeless powder to a point at least as high as that obtained by prior treatments and does this in a fraction of the time and in a much simpler and much more economic way than the prior art methods. My treatment accomplishes in several minutes that which took hours to accomplish before, and at the same time eliminates several expensive steps.

The ethyl alcohol used in my process may be denatured ethyl alcohol, formula #23, containing one-half gallon of benzol per gallons of ethyl alcohol, or denatured ethyl alcohol of other suitable formula.

It will be understood that I am not limited to any particular type press and that various modifications may be made in the above procedure without departing from the spirit thereof and that I do not limit myself to the foregoing examples or descriptions, except as indicated in the following claims.

What I claim and desire to protect by Letters Patent is:

1. The process of restoring the chemical stability of nitrocellulose smokeless powder grains of the Pyro type which have undergone deterioration during storage which comprises subdividing the powder grains under water to a fineness such that they will pass through an 8 mesh screen and be retained on a 200 mesh screen, removing excess water therefrom and then treating said grains under pressure with ethyl alcohol.

2. The process of restoring the chemical stability of nitrocellulose smokeless powder grains of the Pyro type which have undergone deterioration during storage which comprises grinding the powder grains under water to a fineness such that they will pass through an 8 mesh screen and be retained on a 200 mesh screen, removing excess water therefrom and treating said finely divided powder grains under pressure with ethyl alcohol.

3. The process of restoring the chemical stability of nitrocellulose smokeless powder grains of the Pyro type which have undergone deterioration during storage which comprises cracking the powder grains under water to a fineness such that they will pass through an 8 mesh screen and be retained on a 200 mesh screen, removing excess water therefrom and treating said cracked powder grains under pressure with ethyl alcohol.

4. The process of restoring the chemical stability of nitrocellulose smokeless powder grains of the Pyro type which have undergone deterioration during storage which comprises grinding the powder grains under water to a fineness such that they will pass through an 8 mesh screen and be retained on a 200 mesh screen, removing excess water therefrom and treating said finely divided powder grains with ethyl alcohol for about onehalf to about ten minutes under a pressure of about 3000 to 4000 pounds per square inch.

ALPHEUS M. BALL. 

